The present invention concerns variable speed AC driven mining machinery such as crusher mills. Such mills involve massive components and very large horsepower motors in excess of 1000 hp. This type of AC motor sometimes malfunctions in such a way as to create a very large momentary spike in torque sufficient to destroy the pinion ring drives for the mills. This is a catastrophic failure and most require months to bring the equipment back on line.
The industry has previously exclusively used “SAFESET” (trademark of Voith Company of Germany) torque limiters, which are costly and require a long lead time to obtain. They also require part replacements when an overload occurs and involve friction such as to be subject to wear. Ordinary friction torque limiters have been thought to be inadequate for such an application, and shear pins are not consistent in releasing drive and must he replaced.